PHP自动连线依赖项

我正在尝试构建一个依赖项注入容器，它可以使用类型提示自动连接依赖项。当依赖项有自己的依赖项时，问题就会出现。换句话说，我希望依赖项容器能够处理无限嵌套的依赖项

foo Object
(
    [bar] => Bar Object
        (
            [foobar] => foobar Object
                (
                )

        )

)

例如，自动布线这一类将很容易：

class Bar
{
    public function __construct(Foobar $foobar)
    {
        $this->foobar = $foobar;
    }

}

class foo
{
    public function __construct(Bar $bar)
    {
        $this->bar = $bar;
    }
}

现在，如果bar也有依赖项，我必须以某种方式将foobar注入bar，然后再将bar注入foo

class foobar
{

}

class Bar
{
    public function __construct(Foobar $foobar)
    {
        $this->foobar = $foobar;
    }

}


class foo
{
    public function __construct(Bar $bar)
    {
        $this->bar = $bar;
    }
}

---

实现这一点需要两件事：递归和

以下是一个工作示例：

function instantiate($class_name) {
    $reflection = new ReflectionClass($class_name);
    $constructor = $reflection->getConstructor();

    // If there is no constructor in class, return object as is
    if(!$constructor) return $reflection->newInstance();

    $dependencies = [];

    $params = $constructor->getParameters();
    foreach ($params as $param) {
        // Check for type hints in constructor
        $paramType = $param->getClass();
        if($paramType) {
            // If there are type hints, call this very function
            // again (recursion) in order to fetch dependency
            $dependencies[] = instantiate($paramType->name);
        }
    }

    // Return object (resp. dependency if in recursion loop)
    // while also passing required constructor parameters
    return $reflection->newInstanceArgs($dependencies);
}

$foo = instantiate('foo');

如果打印r（$foo），您将看到对象“foo”包含其依赖项

foo Object
(
    [bar] => Bar Object
        (
            [foobar] => foobar Object
                (
                )

        )

)

---

递归肯定是有用的。但实际上，你为什么不去看看一个容器的源代码，看看它是如何实现的呢？